1. Field of the Invention
The present invention relates to a composition for forming a liquid immersion upper layer film, a resist pattern-forming method, a polymer and a compound.
2. Discussion of the Background
In the field of microfabrication typified by production of integrated circuit elements, chemically amplified resists have been conventionally used. In chemically amplified resists, irradiation with, for example, a radioactive ray having a short wavelength such as an excimer laser beam generates an acid at light-exposed sites to cause a difference in rates of dissolution in an alkaline developer solution between light-exposed sites and light-unexposed sites by a reaction by way of the acid as a catalyst, thereby forming a resist pattern on a substrate.
In such chemically amplified resists, as a method for forming a finer resist pattern, the utilization of a liquid immersion lithography process (liquid immersion lithography) is expanding in which exposure is conducted while allowing a liquid immersion media such as, for example, pure water or a fluorine-based inert liquid to be filled in a space between a lens and a resist film. The liquid immersion lithography process allows for an increase in numerical aperture (NA) of the lens, and further provides advantages that, even when the NA is increased, depth of focus is hardly decreased and additionally high resolution can be achieved, and the like.
On the other hand, in the resist pattern formation by the liquid immersion lithography process, it is required to improve its scan speed, while inhibiting pattern defects attributed to elution of a component of the resist film and/or droplets remaining on the surface of the resist film. As a technique for satisfying the requirements, it is proposed to provide a liquid immersion upper layer film between the resist film and a liquid immersion medium (see, Japanese Unexamined Patent Application, Publication No. 2006-91798; PCT International Publication No. 2008/47678; and PCT International Publication No. 2009/41270). These Patent Documents disclose that: the liquid immersion upper layer film is provided on the resist film using a water-insoluble and alkali-soluble polymer; during the liquid immersion lithography, inhibition of the elution of the resist film component and the like is achieved based on the water repellency possessed by the liquid immersion upper layer film; a high scan speed is realized based on a high receding contact angle of the surface of the resist film; and additionally, in a subsequent step of development with an alkali, the liquid immersion upper layer film is peeled from the surface of the resist film by dissolving the liquid immersion upper layer film in a developer solution.
In addition to being excellent in the elution inhibitory property and the performance based on high water repellency such as the high receding contact angle as described above, it is required for the liquid immersion upper layer film to have superior adhesiveness to a peripheral part of a substrate, and to be excellent in peel resistance. Furthermore, for improvement of the process stability, further improvement of the peel resistance is also required.